1. Field of the Invention
This invention relates, generally, to bailers. More particularly, it relates to a bailer that has a cushioned valve assembly at its lowermost end that seals effectively against leakage when seated.
2. Description of the Prior Art
Bailers are elongate cylindrical tubes that are lowered into containers for liquid fluids, bodies of water, and the like for the purpose of taking a sample of the liquid fluid so that laboratory tests can be performed thereon.
In the industry standard bailer, a free-floating ball valve at the lower end of the bailer unseats from its valve seat when the bailer is lowered into a liquid fluid, i.e., as liquid fluid flows upwardly into the hollow interior of the bailer. The ball valve travels downwardly into seating relation to its valve seat when the bailer is lifted upwardly from the liquid fluid. When properly seated, the ball valve should substantially prevent leakage of the liquid fluid from the hollow interior of the bailer.
In practice, however, the ball valve sometimes leaks profusely. The clothing of the person carrying the bailer to a vehicle that will transport the collected sample to a lab often gets wet as the liquid fluid within the bailer leaks past the ball valve. If the liquid fluid is an acid or other irritant, the leakage is more than a mere nuisance. Even if the liquid fluid is just water, the loss of sample is undesireable.
The seat for the ball valve is an annular step formed on an interior surface of a frusto-conical wall that defines the lowermost end of the bailer. A single grain of sand on the annular step can defeat proper seating of the ball valve. Sand and other particulate matter are commonly found in the liquid fluids that are collected by bailers in the field.
Moreover, leakage can occur due to manufacturing imperfections that cause the seating to be less than perfect, even when no particulate matter is present.
An improved bailer, disclosed in the above cross-referenced application, includes a valve seat in the form of an annular concavity formed in an interior surface of the frusto-conical sidewalls. The annular concavity is configured to substantially match an exterior surface of the hemispherical valve body so that substantially no leakage of liquid fluid from the hollow interior of the bailer occurs when the hemispherical valve body is seated against the annular concavity. However, if sand or other particulate matter comes to rest atop the annular concavity, leakage can still result because a single grain of sand can prevent proper seating of the hemispherical ball.
Moreover, manufacturing imperfections in the size and shape of the valve body and its mating valve seat, such as an out-of-round valve body or seat, can cause leakage even where no particulate matter is present in the sample.
The above-mentioned related application also discloses an embodiment where an annular groove of predetermined depth is formed in the interior surface of the frusto-conical sidewalls in an effort to overcome the problems caused by granular material such as sand. The annular groove is in open communication with the annular concavity and is adapted to accommodate at least one grain of a particulate matter so that the at least one grain of particulate matter does not interfere with seating of the hemispherical valve body against the annular concavity.
The formation of the grain-accommodating annular groove in the annular concavity substantially reduces leakage vis a vis the bailers of the prior art, but the manufacturing of the groove adds time and expense to the bailer manufacturing process.
Another drawback of the design disclosed in the related application is that the valve body and valve seat must be manufactured in accordance with relatively strict manufacturing tolerances if the desired seal is to be achieved. If the valve body or valve seat is out-of-round or otherwise malformed, the sealing effectiveness of the design is impaired.
What is needed, then, is an improved valve assembly at the lowermost end of a bailer. The improved valve assembly would not be defeated by a single grain of sand and would not be rendered ineffective by even relatively large amounts of sand. Moreover, it would eliminate the sand-accommodating groove formed in the valve seat. An improved design would also lower the manufacturing tolerance requirements for the valve body and valve seat so that out-of-round or other structural inadequacies could be accommodated without substantial loss in sealing effectiveness.
It was not obvious to those of ordinary skill in this art how an improved, groove-free leak-inhibiting valve for a bailer could be provided, in view of the art considered as a whole at the time the present invention was made.